Lightning arrester and method of making the same



Aug, 23, w32.

J. R. MCFARLIN EA@ LIGHTNING ARRESTER AND METHOD OF MAKING THE SAME Filed Aug. 2, 1926 2 Sheets-Sheet l LIGHTNING RRESTER AND METHOD OF MAKING THE SAME Filed Aug. 2. 1925 f leS-Shee 2 f? r meg.

Patented Aug. 23, 1932 i UNITED STATES PATENT OFFICE JOHN ROBERT MCFARLIN, 0F PHILADELPHIA, PENNSYLVANIA, ASSIGNOR T0 ELECTRIC SERVICE SUPPLIES COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORA- TION OF PENNSYLVANIA lLIGHTNING ARRESTER AND METHOD 0F MAKING THE' SAME Application led August 2, 1926. Serial No. 126,394.

My invention relates to lightning arresters of the air gap type and provides an arrester comprising electrodes having accurately spaced arcing surfaces forming a gap which may be hermetically sealed against the admission of moisture, dust, gas, etc. My invention further pertains to a method of making such arr-esters whereby the bodies of the electrodes are engaged in a firm support and the arcing surfaces thereof are exactly positioned expeditiously, economically and Without necessity for elaborate adjustments.

My improvements are characterized by the provision of the necessary air gap by cutting or forming properly spaced arcing surfaces upon electrode members which have been previously secured in the fixed positions to be occupied thereby in the finished arrester, as contrasted with the practice heretofore of attempting to secure proper spacing by adjustments of the positions of electrodes previously faced or formed to provide arcing surfaces. My invention also involves the positioning of gap-forming electrode members (consisting initially of either integral or separate components) by embedding such members in a plastic dielectric, which.r upon hardening, firmly adheres to and supports the electrode bodies.

In accordance with the preferred practice of my invention, integral or separate conducting members designed to form gap electrodes are first secured in position and a gap formed by cutting or fashioning thereon spaced arcing surfaces which may be readily done by the removal of a conducting section or sections of desired width. as by sawing or drilling, or the electrodes may be spaced by shims during the positioning thereof and the shims withdrawn after the electrodes have been secured. Where comparatively low impedence is desired, the gap is preferably made of such size as will permit insertion in the gap of a plug conductor of predetermined dimensions relatively to the space formed by the cutting, drilling or shimming. For greater accurac the plug preferably abuts against one fixed electrode and is spaced from the other fixed electrode the required distance, but the plug may be so positioned between the fixed electrodes as to provide a gap on either side.

It is generally advantageous to form both fixed electrodes from a single conducting bar, which may be provided with terminal studs and embedded, before severance, in a block of plastic dielectric, which, when hardened, secures the parts in fixed relative positions.

The severance of the Vembedded conductor is preferably effected by drilling through the conductor and into the block to form a passage or chamber in alignment with a passage moulded` in the block and forming a seat for the plug electrode disposed between the fixed electrodes. The plug may be positioned adjacent to one electrode and spaced from the other by a spring clip engaging therewith and with abutments formed in the block, or by providing for the plug base a seat off center from the median line between the fixed electrodes. The carbonization of the dielectric, with consequent fiow of current therethrough from one to the other of the electrodes is prevented or minimized by suitable spacing of the arcing metal members from the dielectric surfaces.

My improved arrester is particularly adapted for the protection of radio antenna, for which exact, accurate and permanent adjustment of the gap is very important. It is, however, suitable for the protection of apparatus connected to alternating current circuits of 115-230 volts, or even higher voltage, to low voltage alternating current signal and alarm circuits, to low voltage direct current circuits, etc.

the length of the The exactness with which the facility with be hermetically air gap may be controlled, which the electrodes may sealed and protected from dust, moisture or corroding gases, and the simplicity, permanence and economy of the device as a whole renders it a very desirable arrester for affording protection against all the phenom- 6 ena of abnormal potential commonly acce ted as being embraced within the term lig tning.

The characteristic features and advantages of my improvements will more fully appear from the following descriptlon and the accompanying drawing illustrating several embodiments of my improved arrester and steps in the manufacture thereof.

In the drawing, Fig. 1 is a longitudinal sectional view of a lightning arrester embodying my improvements, the sealing Wax in the bottom thereof being omitted; Fig. 2 is a top plan view of the arrester shown in Fig. 1; Fig. 3 is a fragmentary view taken on the line indicated by the arrows in Fig. 2 but before the severance of the conductor in the course of manufacture; Fig. 4 is a bottom plan view of the section shown in Fig. 3; Fig. 5 is a perspective view of a conductor with terminal bosses thereon before being embedded in the plastic block; Fig. 6 is a bottom plan view of the conductor shown in Fig. 5 Fig. 7 is a longitudinal sectional view of a dielectric block with a conductor embedded therein suitable for the production of a. modified and preferred form of arrester; Fig. 8 is a transverse sectional View through the center of Fig. 7; Fig. 9 is a bottom plan view of the preferred form of arrester, with the cap for the arc chamber and the sealing wax removed; Fig. 10 is a fragmentary sectional view of the arrester shown in Fig. 9 with the cap closing the arc chamber in place; Fig. 11 is a longitudinal sectional view on a smaller scale than the preceding figures of an unfinished arrester having the arcing surfaces of the electrode members formed by a single narrow saw cut through an integral embedded conducting bar; Fig. 12 is a longitudinal sectional view of an unfinished arrester having arcing surfaces spaced by shims during the moulding in the dielectric of separate electrodes; and Fig. 13 is a longitudinal sectional View of an arrester formed as in Fig. 11 or 12 but with I the gap made of sufficient width to necessitate its reductifi by a plug.

In the preferred practice of my invention, a conducting bar 1, comprising a narrow shank or intermediate section and enlarged end sections, is apertured to form seats for the reduced ends of recessed terminal studs 2, the latter having knurled external surfaces and being rigidly secured to the bar in any suitable manner, as by burring over the exposed edges of the stud ends.

The members 1 and 2 are embedded in a dielectric plastic material, such as bakelite, which is moulded around each member to form, when hardened, a block 3 having the members 1 and 2 securedly positioned therein with the ends of the studs 2 substantially flush with the surface of the block. Apertured lugs 4 are preferably formed on the pe# riphery of the block to provide bearings for fastening screws to secure the arrester in any desired position. The studs 2 are drilled through and tapped for binding posts 5, the latter havin for the attac ment of line and ground wires.

As shown in Figs. 1 to 3, the dielectric block is so moulded, preferably by means of dies, that a hollow recess 7 is formed in the base thereof communicating with passages 8 below the studs 2. The median portion of the bottom of the block, which may bulge as at 9, is recessed to form circular passageways or seats 10 and 11 having their centers eccentric to one another. The conductor 1 is severed (or if separate pieces are used they are cut) preferably by drilling therethrough into the block 3, so as to form spaced arcing surfaces 1a and 1b in substantial alignment with diametric sections of the passageway 11. The space between the electrodes is preferably reduced to the desired gap width by inserting therein the projecting tongue 12 on the base 13 of a conducting plug conforming with and tightly forced into the seat 10. The width of the tongue 12 is suitably proportioned to the space between the parts la and 1b; the tongue being preferably centered on the plug base so that it engages the gap electrode 1a but is spaced from the electrode 1b the distance necessary for preventing flow of normal current through the arrester. The tongue may be made of any desired shape, but is preferably flat so as to make minimum contact with the dielectric and avoid carbonization of the bakelite, which may render the latter conductive.

When the plug electrode has been positioned, the hollow base of the block and the passageways communicating therewith are filled with dielectric Sealing material, such as wax, so that the conducting members other than the line terminals are hermetically sealed and deterioration thereby prevented.

As illustrated in Figs. 7, 8, 9 and 10, the arrester may be more economically and accurately made and carbonization of the dielectric block may be further minimized and the positioning of the plug electrode improved by recessing the base of the block 3 to form a gap chamber 14 containing a rib or ledge 15 embedding the shank of the bar 1. The lateral walls of an enlarged section 16 of the gap chamber have projections or abutments 17 thereon providing anchorages for the ends of a spring clip 18 securing in place a conducting cylindrical plug 12a, the latter containing a peripheral groove for the engagement of the clip. A plate or cap 19 closes the chamber containing the plug.

It will be understood that the conducting thereon the lipped washers 6 of the gap avoided. When the plug electrode 12a has been positioned so as to contact with one electrode 1a. and be spaced from the other electrode 1b, the cover 19 is snapped into its seatand the base of the arrester is filled with a suitable non-conducting composition which hermetically seals the parts.

As illustrated in Fig. 11, the dielectric block is so moulded as to form a chamber at the center of the bar 1, which is severed by a saw cut of a proper thickness to form the desired gap. 'Ihe chamber may be closed by a cap 19. t

As illustrated in Fig. 12, the dielectric block is moulded and hardened around bar sections 1 spaced by shims 20 of suitable thickness.

As illustrated in Fig. 13, the bar of Fig. 11 may be sulliciently cut away or the bar Sections of Fig. 12 may be sufiiciently spaced to necessitate the insertion of a plug similar to the plug of Fig. l, or a plug and cap similar to those shown in Fig. 10 may be used to reduce the space between the arcing surfaces.

It will be obvious that the principles of my invention are not limitedto the specific forms of arresters shown and described by way of illustration but are susceptible of various modifications and changes without departing from the spirit of my invention as defined in the appended claims.

Having described I ny invention, I claim,

1. A lightning arrester comprising a plurality' of electrode members secured to a dielectric bythe adhesion thereof, said electrode members having faces spaced to form a gap, and a conducting member disposed in said gap and contacting with one of said faces.

2. -A lightning arrester comprising a hardened dielectric plastic block having embedded immovably therein a conductor having spaced elements forming a gap, and a plug secured in said gap and disposed between the ends of said conductor elements and contacting with one of said spaced ends.

3. A lightning arrester including a plurality of conducting sections with a gap between them, a holder for said sections containing a passage communicating with said gap and having a plug seated in said passage in contact with one of said conductin members and spaced from the other thereof.

4i A lightning arrester including a dielectric block having embedded therein a plurality of spaced electrode members with a gap between them, a plug disposed between said electrodes, and means for forcing said plug toward one of said electrodes.

5. A hghtning arrester including a block of hardened dielectric plastic having immovably embedded therein a conductor comprising spaced elements and having terminals disposed transversely thereto and extending through said block, a plug disposed between the spaced sections of said conductor and contacting with one of said sections, and means for sealing said plug in said block.

6. A lightning arrester including a dielectric block having gap electrodes secured therein and a plug seated in said block and disposed between said electrodes, and means for positioning said plug relatively to said electrodes and including a spring seated in said block.

7. A lightning arrester including a dielectric block having gap electrodes embedded therein and containing a chamber, a plug disposed in said chamber between said electrodes, a clip anchored in said block for positioning said plug, and means for sealing said chamber.

8. The step in the method of forming lightning arresters which comprises cutting previously fixed electrode means to form a spark gap.

9. The step in the method of forming lightning arresters which comprises inserting a plug between fixed electrode means spaced to form a gap between said plug and one or more of said electrode members.

10. The method of forming a spark gap for a lightning arrester which comprises securing conducting means in the positions to be occupied thereby in the finished arrester and cutting such positioned means to form a desired space between them.

11. The method of forming a spark gap for a lightning arrester which comprises securing conductor means in the positions t0 be occupied thereby in the finished arrester, severin said conductor members to form a gap, an inserting a conducting device in the space between such conductor means.

12. The method of forming a lightning arrester which comprises .securing a conductor in a hardened plastic dielectric vand forming a gap by severing such conductor.

13. The method of forming a lightning arrester which comprises embedding a vconductor in a plastic dielectric, hardening the dielectric, severing the conductor, and securing between the severed sections a conducting member spaced from one of said sections.

14. In the method of forming arresters, the step which comprises cutting a previously fixed electrode into members to form a spark gap.

` 15. In the method of forming a spark gap for lightning arresters, the step which comprises securing a conducting member in the lightning position to be occupied by portions thereof in the finished arrester and cuttin such ositioned member to form a desire space tween said portions.

16. The method of forming a spark gap for a lightning arrester which comprises securing a conductor in the position to be occupied by parts thereof in the finished arrester, severing said conductor to form a ap, and inserting a, conducting device in t e space between such parts.

In testimony whereof 1 have hereunto set my hand this 20th day of July, 1926.

JOHN ROBERT MCFARLIN. 

